Fullerene up-take alters bilayer structure and elasticity: A small angle X-ray study

Abstract

The coupling of fullerene (C 60 ) to the structure and elasticity of 1-palmitoyl-2-oleoyl-snglycero-3-phosphocholine bilayers has been explored by synchrotron small angle X-ray scattering. Multilamellar vesicles were loaded with 0, 2 and 10 mol. % of C 60 and studied in a temperature range from 15-65°C. The addition of C 60 caused an increase in the bilayer undulations (~20 %), in the bilayer separation (~15%), in the linear expansion coefficient and caused a drop in the bending rigidity of the bilayers (20-40 %). Possible damaging effects of fullerene on biomembranes are mainly discussed on the basis of altered bilayer fluidity and elasticity changes.

Effect of fullerene on the dispersibility of nanostructured lipid particles and encapsulation in sterically stabilized emulsions

“…Spontaneous aggregation and clustering of fullerenes in aqueous media has been discussed by several researchers [7,14,41,42]. Agglomeration and surface 6 adhesion has also been demonstrated with surfactant micellar systems, cellular membranes as well as model lipid bilayers [6,8,12,14]. 25 g/ml C60 were produced successfully, however lower C60 concentrations struggled to form under similar experimental conditions.…”

“…The fullerene or aggregates are decorated, in principle, by hydrophobic lipid chains (facing fullerenes) while hydrophilic head groups face an aqueous environment [10]. Stabilization may also occur due to the spontaneous penetration of fullerenes in lipid bilayers, which ideally form a part of liposomes (vesicles) [8,46] (Figure 5a). Fullerene insertion in bilayers was previously investigated by several researchers [6,[8][9][10][12][13][14].…”

“…Fullerene insertion in bilayers was previously investigated by several researchers [6,[8][9][10][12][13][14]. Aforementioned low (0.1%) lipid dispersions were stable, but 5% lipid dispersions prepared using various fullerene concentrations faced severe destabilization which can be attributed partially to the following aspects: 1) self-aggregation of fullerenes in aqueous media [7,42,47], 2) adhesion of fullerenes to lipid membranes [8,10,46], 3) penetration of fullerenes [8] and/or small clusters [10] in membranes, 4) apparent high viscosity of liquid crystalline phase and 5) layer-by-layer growth of above aggregates during cooling and/or vigorous shaking where initial clusters act as templates (or nuclei) for the adhesion of additional layers [10]. However, these aspects need further confirmation with detail investigations.…”

“…Some synthetic chemists, working in this direction, have been able to functionalize fullerenes and obtain their water-soluble derivatives [4,7]. However, in order to understand the biological activity of fullerenes and their potential therapeutic role, it is important to investigate their interactions with cellular membranes [8] than just solubility studies.…”

“…Considerable theoretical (simulation-based) [9][10][11][12][13] and experimental [8,14] efforts have been taken to investigate fullerene interactions with biological as well as artificial membrane systems. These reports mainly involved studies with planar lipid bilayers, spherical micelles or vesicles.…”